1. Field of the Invention
The present invention relates to an apparatus for transporting sheets of paper, for example, for use in copying machines, printers and automatic document feeders (ADFs). The present invention also relates to correction of the timer value with time for detecting jams.
2. Description of the Prior Art
For example with copy paper feeding apparatus for copying machines, it is practice to detect paper jams with use of a constant-time timer (hereinafter referred to as a "jam timer").
For example when copy paper fails to reach a specified position (e.g. the position of a sensor provided upstream of a timing roller) within a period of time determined by the jam timer after the feed roller for delivering the copy paper from a paper cassette is initiated into rotation, the failure is interpreted as indicating occurrence of a jam, and the copying machine is brought into a stand-by state or the like for the treatment of the jam.
However, the feed roller is adapted to transport copy paper by friction in pressing contact therewith and thereflore slips when becoming worn, delaying the arrival time of the copy paper and allowing the jam timer to detect a paper jam.
If the wear of the roller is slight, such a delay causes no particular trouble to copying operation, whereas the convention copying machine is stopped by the delay although operable free of trouble, causing inconvenience to the user.
The objection described is not limited only to the use of the roller serving as transport means but is also encountered with other transport means such as conveyor belts when the movable portion wears.